22 of Muhammad Ali's greatest quotes of all time

Muhammad Ali, one of the world's greatest boxers, died on Friday, June 3, at the age of 74.

Born Cassius Marcellus Clay on January 17, 1942, in Louisville, Kentucky, Ali started boxing at age 12 — and ultimately became known for much more than just his successful boxing career.

Ali converted to Islam in 1964, changing his name from Cassius Clay — what he called his "slave name" — to Muhammed Ali after becoming affiliated with the Nation of Islam. His political activism and charity inspired millions throughout his life.

We've compiled some of his now iconic words of wisdom and trademark boxing-ring rhymes.

"If they can make penicillin out of moldy bread, they can sure make something out of you."

In this November 15, 1962, file photo, young heavyweight boxer Cassius Clay points to a sign he wrote on a chalk board in his dressing room before his fight against Archie Moore in Los Angeles, predicting he'd knock Moore out in the fourth round, which he went on to do. The sign also predicts Clay will be the next champ via a knockout over Sonny Liston in eight rounds. He did it in seven rounds.AP Photo/Harold P. Matosian, File

"Friendship is the hardest thing in the world to explain. It's not something you learn in school. But if you haven't learned the meaning of friendship, you really haven't learned anything."

"The best way to make your dreams come true is to wake up."

Muhammad Ali (Cassius Clay), the "Louisville lip," holds up eight fingers in London June 19, 1963 as he predicts the number of rounds it will take him to knock out Sonny Liston if he should get a chance at the world heavyweight championship. Clay had predicted an end to his fight with British heavyweight champion Henry Cooper in five rounds and that's just what happened June 18 in London's Wembley stadium. Ali won on a technical knockout in the fifth round.AP Photo

"He who is not courageous enough to take risks will accomplish nothing in life."

Perspiration beads on the face of world heavyweight boxing champion Muhammad Ali, shown in training for his May 25, 1965, fight with Sonny Liston at Lewiston, Maine.AP Photo

"Now Clay swings with a right, what a beautiful swing/And the punch raises the Bear clear out of the ring/ Liston is still rising, and the ref wears a frown/For he can't start counting `til Sonny comes down/Now Liston disappears from view."

Heavyweight champion Muhammad Ali stands over fallen challenger Sonny Liston, shouting and gesturing shortly after dropping Liston with a short, hard right to the jaw on May 25, 1965, in Lewiston, Maine.AP Photo/John Rooney

"I hated every minute of training, but I said, ‘Don’t quit. Suffer now and live the rest of your life as a champion.'"

Muhammad Ali, Cassius Clay at the time, strikes a familiar pose as he shouts, "I am the greatest," as he leaves the ring, arms raised, following his defeat of former heavyweight boxing champion Sonny Liston in Miami Beach, Florida, February 25, 1964.AP Photo

"I know where I’m going and I know the truth, and I don’t have to be what you want me to be. I’m free to be what I want."

"To be a great champion you must believe you are the best. If you’re not, pretend you are."

Cassius Clay after being declared heavyweight champion of the world at Miami Beach, Florida, February 25, 1964. Clay beat champion Sonny Liston after six rounds in one of the greatest upsets in fight history.AP Photo/stf

"I am the greatest. I said that even before I knew I was. I figured that if I said it enough, I would convince the world that I really was the greatest

A September 12, 1974, file photo of Muhammad Ali, who was due to fight World Champion George Foreman, tells a crowd of boxing fans in N' Sele Zaire, "Ako bo mai ye," which translates from Zaire's Lingalla dialect as: "I will kill him."AP Photo/Horst Faas, Fil

"Impossible is just a big word thrown around by small men who find it easier to live in the world they've been given than to explore the power they have to change it. Impossible is not a fact. It's an opinion. Impossible is not a declaration. It's a dare. Impossible is potential. Impossible is temporary. Impossible is nothing."

Heavyweight boxer Muhammad Ali makes a point during a news conference that he conducted from inside the ring in Atlanta, Georgia, in this October 24, 1970, file photo.AP Photo/FILE

Spray flies from the head of challenger Joe Frazier as heavyweight champion Muhammad Ali connects with a right in the ninth round of their title fight in Manila, Philippines, October 1, 1975. Ali won the fight on a decision to retain the title.AP Photo/Mitsunori Chigit

"Champions aren’t made in gyms. Champions are made from something they have deep inside them—a desire, a dream, a vision. They have to have last-minute stamina, they have to be a little faster, they have to have the skill and the will. But the will must be stronger than the skill."

With compressed lips, Muhammad Ali punches bag on January 10, 1974, in his Deer Lake, Pennsylvania, training camp, where he was preparing for his January 28 rematch with Joe Frazier.AP Photo/ Rusty Kennedy

"You think the world was shocked when Nixon resigned?/Wait `til I whup George Foreman's behind./Float like a butterfly, sting like a bee./His hand can't hit what his eyes can't see."

An October 30, 1974, file photo of Muhammad Ali as he watches George Foreman head for the canvas after being knocked out in the eighth round of their match in Kinshasa, Zaire. It was 41 years ago that two men met just before dawn on Oct. 30, 1974, to earn $5 million in the Rumble in the Jungle. In one of boxing's most memorable moments, Muhammad Ali stopped the fearsome George Foreman to recapture the heavyweight title in the impoverished African nation of Zaire.AP Photo

"Now you see me, now you don't.George thinks he will, but I know he won't.I done wrassled with an alligator, I done tussled with a whale.Only last week I murdered a rock, injured a stone, hospitalized a brick.I'm so mean, I make medicine sick."

"I got speed and endurance./You'd better increase your insurance."

Muhammad Ali, world heavyweight champion, punches speed bag on September 29, 1975 at the Folk Art Center in Manila, Philippines, as he prepares his title fight on October 1 with Joe FrazierAP Photo/Jess Tan

"What you're thinking is what you're becoming."

Muhammad Ali is seen prior to the first round of his title fight against heavyweight contender Ken Norton, shouting "Norton must fall" at Yankee Stadium in New York on Tuesday, September 28, 1976. Days later on Friday, October 1, in Istanbul, Ali told a crowd of reporters and photographers that "as of now, I am quitting boxing and will devote all my energy to the propagation of the Muslim faith."AP Photo

"Live everyday as if it were your last because someday you're going to be right."

"The man who views the world at 50 the same as he did at 20 has wasted 30 years of his life."

Muhammad Ali receives a replacement gold medal for one he lost many years ago during a halftime ceremony of the Yugoslavia vs. USA basketball game at the Georgia Dome at the 1996 Centennial Olympic Games in Atlanta, Georgia.Getty Images/Doug Pensinger

"Hating people because of their color is wrong. And it doesn't matter which color does the hating. It's just plain wrong."

"Don't count the days, make the days count."

Muhammad Ali onstage during the Michael J. Fox Foundation's 2010 Benefit "A Funny Thing Happened on the Way to Cure Parkinson's" at The Waldorf-Astoria on November 13, 2010, in New York City.Getty Images/Andrew H. Walker